A method for preparing highly oriented graphite films using small molecule saccharide substances

Abstract

A method for preparing highly oriented graphite films using small molecule saccharide substances. This invention belongs to the field of carbon material preparation. The purpose of this invention is to solve the problems of high production difficulty, high production cost and easy environmental pollution in the production of highly oriented graphite films. The method includes: First, preparing a saccharide precursor solution; Second, spin-coating to form a film; Third, gelation; Fourth, pre-carbonization and carbonization; Fifth, graphitization. This invention has created a precedent for preparing highly oriented graphite films using saccharide substances. The prepared highly oriented graphite films have extremely high purity, good crystallinity, high graphitization degree, obvious oriented structure, and have high practical application and scientific research value. The highly oriented graphite films prepared by this invention have relatively excellent electromagnetic shielding performance. The prepared 650nm thick highly oriented graphite film has an electromagnetic shielding performance exceeding 50dB in the X-band.

Description

Technical Field

[0001] The present invention belongs to the field of carbon material preparation, and particularly relates to a method for preparing highly oriented graphite films using small molecule saccharide substances. Background Art

[0002] Highly oriented graphite films are a type of crystalline graphite with good crystallization quality, extremely strong layer orientation, and a high degree of graphitization. Due to the orderly stacking of graphene sheets inside, they have typical anisotropic thermal conductivity and high electrical conductivity, and play an important role in fields such as electromagnetic shielding, flexible electronic devices, efficient thermal management, and energy. Because highly oriented graphite films have an approximately ideal graphite structure, they are even used as standard samples for scanning tunneling microscopes and key components of monochromators, playing an important role in scientific research, instrument manufacturing, and industrial production.

[0003] Currently, highly oriented graphite films are mainly obtained by chemical vapor deposition of high-purity hydrocarbon compounds (such as methane, acetylene, benzene, etc.), high-temperature pyrolysis of petroleum-based polymers (such as polyimide, pitch, etc.), or direct assembly and reduction of graphene oxide. However, the production conditions of the vapor deposition method are harsh, the production efficiency is low, and the cost is relatively high. The raw materials of polymers all come from petrochemical industry. As the development of petroleum resources is exhausted, the price will further increase. At the same time, the waste generated during the manufacturing process has a great harm to the environment. Although the method of assembling graphene oxide has a relatively simple preparation process, the internal structural integrity of graphene oxide with good dispersion performance is poor, and the production process of high-quality graphene is extremely complex, the production cost remains high, and at the same time, waste that pollutes the environment will also be generated. Therefore, it is very necessary to develop green, environmentally friendly, and renewable biomass-based highly oriented graphite materials, which can not only solve environmental pollution problems, but also reduce manufacturing costs to a certain extent.

[0004] Saccharide substances are an important class of carbohydrates widely distributed in nature, can be extracted from plants in nature, belong to a renewable resource, and the price of saccharide substances is low and purification is relatively easy, which is an ideal carbon raw material. However, small molecule saccharides such as glucose, fructose, sucrose, and maltose are considered to be carbon that is difficult to graphitize, and uncontrollable foaming will occur during the carbonization process. Therefore, small molecule saccharide substances are generally only suitable for preparing porous carbon materials, and there is no relevant report on preparing highly oriented dense graphite materials using small molecule saccharides. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing highly oriented graphite films using small molecule saccharide substances in order to solve the problems of high production difficulty, high production cost, and easy environmental pollution in the production of highly oriented graphite films.

[0006] The present invention for the first time uses small molecule saccharide substances as carbon sources to prepare highly oriented graphite films. The prepared graphite films are uniformly dense inside, with obvious oriented structures and good crystallinity. Almost all raw materials used in the present invention are non-toxic, harmless, green and environmentally friendly, and the operation is convenient and the equipment is simple, greatly reducing the manufacturing cost of highly oriented graphite films, providing new ideas and solutions for the research and development of anisotropic structured graphite materials, and at the same time creating conditions for the application expansion of high-performance graphite materials.

[0007] A method for preparing highly oriented graphite films using small molecule saccharide substances is realized according to the following steps:

[0008] I. Prepare a saccharide precursor solution:

[0009] Mix deionized water, water-soluble saccharides, acrylamide, and N,N'-methylenebisacrylamide in a certain proportion and stir to obtain a clear saccharide precursor solution;

[0010] II. Spin-coat to form a film:

[0011] Drop the clear saccharide precursor solution onto a single crystal silicon wafer and use a spin coater to prepare a liquid film with a certain thickness at a certain spin coating speed;

[0012] III. Gelation:

[0013] Transfer the single crystal silicon wafer and the liquid film in step II to a heating table to cause the acrylamide gel system in the solution to gelate, and the liquid film is transformed into a hydrogel film;

[0014] IV. Pre-carbonization and carbonization:

[0015] Perform low-temperature pre-carbonization and high-temperature carbonization on the hydrogel film to obtain a carbon film with an oriented structure;

[0016] V. Graphitization:

[0017] Chemically peel the carbon film with an oriented structure from the single crystal silicon wafer, and perform graphitization on the peeled carbon film in an intermediate frequency induction furnace to obtain a highly oriented graphite film.

[0018] Advantages of the present invention:

[0019] (1). The present invention creates a precedent for preparing highly oriented graphite films using saccharide substances. The prepared highly oriented graphite films have extremely high purity, good crystallinity, high graphitization degree, obvious oriented structures, and have high practical application and scientific research value;

[0020] (2) The main raw materials used in the preparation process of the highly oriented graphite film provided by the present invention are green, environmentally friendly, non-toxic, harmless and low in price. The preparation process of the polymer precursor with a high degree of polymerization is transformed into a simple purification process of saccharide substances, providing a new solution for the preparation of high-quality graphite materials with a highly oriented structure.

[0021] (3) The graphite material preparation process provided by the present invention is simple. The graphite structure is uniform, dense and has good integrity, with excellent thermal and electrical conductivity, as well as high-efficiency electromagnetic shielding performance and high mechanical properties. It is expected to be used as a high-performance wide-temperature-range thermal conductive material and electromagnetic shielding material in the fields of electronics, automobiles, aerospace, etc., and has broad market prospects.

[0022] (4) The highly oriented graphite film prepared by the present invention has relatively excellent electromagnetic shielding performance. The prepared highly oriented graphite film with a thickness of 650 nm has an electromagnetic shielding performance exceeding 50 dB in the X band. Description of the Drawings

[0023] Figure 1 SEM micrograph of the cross-section of the highly oriented graphite film prepared in Example 1;

[0024] Figure 2 TEM micrograph of the highly oriented graphite film prepared in Example 1;

[0025] Figure 3 XRD pattern of the highly oriented graphite film prepared in Example 1;

[0026] Figure 4 Raman spectrum of the highly oriented graphite film prepared in Example 1;

[0027] Figure 5 Electromagnetic shielding performance test chart of the highly oriented graphite film prepared in Example 1 in the X band;

[0028] Figure 6 SEM micrograph of the cross-section of the highly oriented graphite film prepared in Example 2;

[0029] Figure 7 TEM micrograph of the highly oriented graphite film prepared in Example 2. Detailed Embodiments

[0030] Detailed Embodiment 1: A method for preparing a highly oriented graphite film using small molecule saccharide substances is achieved according to the following steps:

[0031] I. Prepare a saccharide precursor solution:

[0032] Mix deionized water, water-soluble sugars, acrylamide, and N,N'-methylenebisacrylamide in a certain ratio and stir to obtain a clear sugar precursor solution;

[0033] II. Spin-coating to form a film:

[0034] Drop the clear sugar precursor solution onto a single-crystalline silicon wafer and prepare a liquid film with a certain thickness at a certain spin-coating speed using a spin coater;

[0035] III. Gelation:

[0036] Transfer the single-crystalline silicon wafer and the liquid film from step II to a heating stage to cause the acrylamide gel system in the solution to gelate, and the liquid film is transformed into a hydrogel film;

[0037] IV. Pre-carbonization and carbonization:

[0038] Perform low-temperature pre-carbonization and high-temperature carbonization on the hydrogel film to obtain a carbon film with an oriented structure;

[0039] V. Graphitization:

[0040] Chemically peel the carbon film with an oriented structure from the single-crystalline silicon wafer, and perform graphitization on the peeled carbon film in a medium-frequency induction furnace to obtain a highly oriented graphite film.

[0041] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: the mass ratio of the water-soluble sugars to deionized water in step I is (1-4):1; the mass ratio of acrylamide to water-soluble sugars in step I is (0.1-0.5):1; the mass ratio of N,N'-methylenebisacrylamide to acrylamide in step I is (0.01-0.1):1. Other steps are the same as those in Specific Embodiment 1.

[0042] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that: the water-soluble sugars in step I are one or a mixture of water-soluble glucose, water-soluble fructose, water-soluble sucrose, and water-soluble maltose. Other steps are the same as those in Specific Embodiment 1 or 2.

[0043] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that: the stirring time in step I is 30 min - 60 min, and the stirring speed is 200 r / min - 400 r / min; the spin-coating speed in step II is 1000 r / min - 10000 r / min, and the spin-coating time is 20 s - 40 s. Other steps are the same as those in Specific Embodiments 1 to 3.

[0044] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that: the temperature of gelation in Step 3 is 70°C to 100°C, and the time of gelation is 10 min to 30 min. Other steps are the same as those in Specific Embodiments 1 to 4.

[0045] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that: the low-temperature pre-carbonization in Step 4 is to heat the hydrogel film from room temperature to 150°C to 300°C at a heating rate of 1°C / min to 5°C / min, and carbonize it at 150°C to 300°C for 1 h to 24 h to obtain a film after low-temperature pre-carbonization. Other steps are the same as those in Specific Embodiments 1 to 5.

[0046] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that: the temperature of high-temperature carbonization in Step 4 is 800°C to 1400°C, and the time of high-temperature carbonization is 1 h to 24 h to obtain a carbon film with an oriented structure. Other steps are the same as those in Specific Embodiments 1 to 6.

[0047] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that: the atmosphere of high-temperature carbonization in Step 4 is vacuum or inert gas; the inert atmosphere is argon. Other steps are the same as those in Specific Embodiments 1 to 7.

[0048] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that: the atmosphere of graphitization in Step 5 is vacuum or inert atmosphere; the inert atmosphere is argon. Other steps are the same as those in Specific Embodiments 1 to 8.

[0049] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 9 is that: the temperature of graphitization in Step 5 is 2400°C to 3000°C, and the time of graphitization is 3 h to 24 h. Other steps are the same as those in Specific Embodiments 1 to 9.

[0050] The following examples are used to verify the beneficial effects of the present invention:

[0051] Example 1: A method for preparing a highly oriented graphite film using small molecule saccharide substances is realized according to the following steps:

[0052] I. Prepare a saccharide precursor solution:

[0053] Mix 15 g of deionized water, 35 g of water-soluble glucose, 7 g of acrylamide, and 0.35 g of N,N'-methylenebisacrylamide, and stir at a stirring speed of 300 r / min for 60 min to obtain a clear saccharide precursor solution;

[0054] II. Spin-coat to form a film:

[0055] The clarified sugar precursor solution was dropped onto a single-crystalline silicon wafer and spin-coated for 15 s at a speed of 3000 r / min by a spin coater to prepare a liquid film with a certain thickness.

[0056] III. Gelation:

[0057] The single-crystalline silicon wafer and the liquid film in Step II were transferred to a heating table to cause gelation of the acrylamide gel system in the solution, and the liquid film was transformed into a hydrogel film.

[0058] The temperature of the gelation described in Step III was 80 °C, and the gelation time was 15 min.

[0059] IV. Pre-carbonization and carbonization:

[0060] The hydrogel film was subjected to low-temperature pre-carbonization and high-temperature carbonization to obtain a carbon film with an oriented structure.

[0061] The low-temperature pre-carbonization described in Step IV was to heat the hydrogel film in air from room temperature to 200 °C at a heating rate of 1 °C / min and carbonize it at 200 °C for 3 h to obtain a film after low-temperature pre-carbonization.

[0062] The high-temperature carbonization described in Step IV was to place the film after low-temperature pre-carbonization in a vacuum atmosphere cracking furnace at 1400 °C for carbonization treatment for 1 h to obtain a carbon film with an oriented structure.

[0063] V. Graphitization:

[0064] The carbon film with an oriented structure was chemically peeled off from the single-crystalline silicon wafer, and the peeled carbon film was placed in an inert atmosphere graphitization furnace at 3000 °C for graphitization treatment for 3 h to obtain a highly oriented graphite film. The cross-sectional micro-morphology of the highly oriented graphite film is as Figure 1 shown;

[0065] The inert atmosphere described in Step V was an argon atmosphere.

[0066] Figure 1 It is the SEM cross-sectional micrograph of the highly oriented graphite film prepared in Example 1;

[0067] From Figure 1 it can be seen that: an obvious graphite sheet layer oriented structure.

[0068] The thickness of the highly oriented graphite film prepared in Example 1 was 650 nm. The TEM of the graphite material is as Figure 2 shown;

[0069] Figure 2 It is the micro-TEM image of the highly oriented graphite film prepared in Example 1;

[0070] From Figure 2 it can be seen that the lattice fringes of the (002) crystal plane are parallel to each other, and the arrangement of carbon atoms has obvious directionality and obvious orientation structure.

[0071] Figure 3 is the XRD pattern of the highly oriented graphite film prepared in Example 1;

[0072] From Figure 3 it can be seen that the crystallization quality of the highly oriented graphite film prepared in Example 1 is good.

[0073] Figure 4 is the Raman pattern of the highly oriented graphite film prepared in Example 1;

[0074] From Figure 4 it can be seen that the highly oriented graphite film prepared in Example 1 has almost no defects and has high quality.

[0075] From Figure 3 the XRD pattern of Figure 4 and the Raman pattern information of

[0076] Figure 5 it can be seen that the highly oriented graphite film prepared in Example 1 has excellent electromagnetic shielding performance. The 650-nm-thick highly oriented graphite film prepared has an electromagnetic shielding performance exceeding 50 dB in the X band.

[0077] From Figure 5 it can be seen that the highly oriented graphite film prepared in Example 1 has relatively excellent electromagnetic shielding performance. The 650-nm-thick highly oriented graphite film prepared has an electromagnetic shielding performance exceeding 50 dB in the X band.

[0078] Example 2: A method for preparing a highly oriented graphite film using small molecule saccharide substances is realized according to the following steps:

[0079] I. Prepare a saccharide precursor solution:

[0080] Mix 15 g of deionized water, 40 g of water-soluble fructose, 8 g of acrylamide, and 0.4 g of N,N'-methylenebisacrylamide, and stir at a stirring speed of 300 r / min for 60 min to obtain a clear saccharide precursor solution;

[0081] II. Spin-coat to form a film:

[0082] Drop the clear saccharide precursor solution onto a single-crystalline silicon wafer, and spin-coat it at a rotation speed of 3000 r / min for 15 s using a spin coater to prepare a liquid film with a certain thickness;

[0083] III. Gelatinization:

[0084] Transfer the single-crystalline silicon wafer and the liquid film from Step II to a heating stage to cause the acrylamide gel system in the solution to gelatinize, and the liquid film is transformed into a hydrogel film;

[0085] The temperature of the gelatinization described in Step III is 80 °C, and the time of gelatinization is 15 min;

[0086] IV. Pre-carbonization and carbonization:

[0087] Perform low-temperature pre-carbonization and high-temperature carbonization on the hydrogel film to obtain a carbon film with an oriented structure;

[0088] The low-temperature pre-carbonization described in Step IV is to heat the hydrogel film in air from room temperature to 200 °C at a heating rate of 1 °C / min and carbonize it at 200 °C for 3 h to obtain a film after low-temperature pre-carbonization;

[0089] The high-temperature carbonization described in Step IV is to place the film after low-temperature pre-carbonization in a vacuum atmosphere cracking furnace at 1400 °C for carbonization treatment for 1 h to obtain a carbon film with an oriented structure;

[0090] V. Graphitization:

[0091] Chemically peel the carbon film with an oriented structure from the single-crystalline silicon wafer, and place the peeled carbon film in an inert atmosphere graphitization furnace at 3000 °C for 3 h of graphitization treatment to obtain a highly oriented graphite film.

[0092] Figure 6 SEM micrograph of the microscopic cross-section of the highly oriented graphite film prepared in Example 2;

[0093] From Figure 6 it can be seen that there is an obvious oriented structure of graphite sheets.

[0094] The thickness of the highly oriented graphite film prepared in Example 2 is about 850 nm. Combining with the TEM of the graphite material as Figure 7 shown;

[0095] Figure 7 TEM micrograph of the microscopic view of the highly oriented graphite film prepared in Example 2;

[0096] From Figure 7 it can be known that the lattice fringes of the (002) crystal plane are parallel to each other, the arrangement of carbon atoms has obvious directionality, and there is an obvious oriented structure.

Claims

1. A method for preparing highly oriented graphite films using small molecular saccharides, characterized in that The highly oriented graphite film prepared by this preparation method has good crystallization quality. The lattice fringes of the (002) crystal plane are parallel to each other, the arrangement of carbon atoms has obvious directionality, and it has an obvious orientation structure; The said preparation method is realized according to the following steps: I. Prepare a saccharide precursor solution: Mix deionized water, water-soluble saccharides, acrylamide, and N,N'-methylenebisacrylamide in a certain ratio and stir to obtain a clear saccharide precursor solution; In step I, the mass ratio of the water-soluble saccharides to deionized water is (1-4):1; in step I, the mass ratio of acrylamide to water-soluble saccharides is (0.1-0.5):1; in step I, the mass ratio of N,N'-methylenebisacrylamide to acrylamide is (0.01-0.1):1; II. Spin-coat to form a film: Drop the clear saccharide precursor solution onto a single-crystal silicon wafer and prepare a liquid film with a certain thickness through a spin coater at a certain spin coating speed; III. Gelation: Transfer the single-crystal silicon wafer and the liquid film in step II to a heating table to cause the acrylamide gel system in the solution to gelate, and the liquid film is transformed into a hydrogel film; In step III, the temperature of the gelation is 70°C - 100°C, and the time of gelation is 10 min - 30 min; IV. Pre-carbonization and carbonization: Perform low-temperature pre-carbonization and high-temperature carbonization on the hydrogel film to obtain a carbon film with an orientation structure; V. Graphitization: Chemically peel the carbon film with an orientation structure from the single-crystal silicon wafer, and perform graphitization on the peeled carbon film in an intermediate-frequency induction furnace to obtain a highly oriented graphite film; In step V, the atmosphere for graphitization is a vacuum or an inert atmosphere; the said inert atmosphere is argon; In step V, the temperature of graphitization is 2400°C - 3000°C, and the time of graphitization is 3 h - 24 h.

2. The method for preparing a highly oriented graphite film using small molecule saccharide substances according to claim 1, wherein The water-soluble saccharides described in step I are one or a mixture of several of water-soluble glucose, water-soluble fructose, water-soluble sucrose, and water-soluble maltose.

3. A method for preparing highly oriented graphite films using small molecule saccharides according to claim 1, characterized in that In step I, the stirring time is 30 min - 60 min, and the stirring speed is 200 r / min - 400 r / min; in step II, the spin coating speed is 1000 r / min - 10000 r / min, and the spin coating time is 20 s - 40 s.

4. A method for preparing a highly oriented graphite film using small molecule saccharide substances according to claim 1, characterized in that The low-temperature pre-carbonization described in step IV is to heat the hydrogel film from room temperature to 150°C - 300°C at a heating rate of 1°C / min - 5°C / min and carbonize it at 150°C - 300°C for 1 h - 24 h to obtain a film after low-temperature pre-carbonization.

5. A method for preparing highly oriented graphite films using small molecule saccharide substances according to claim 1, characterized in that The temperature of the high-temperature carbonization described in step IV is 800°C - 1400°C, and the time of high-temperature carbonization is 1 h - 24 h to obtain a carbon film with an orientation structure.

6. A method for preparing a highly oriented graphite film using small molecule saccharide substances according to claim 1, characterized in that The atmosphere for the high-temperature carbonization described in step IV is a vacuum or an inert gas; the said inert atmosphere is argon.

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